Disruption of protein kinase A interaction with A-kinase-anchoring proteins in the heart in vivo: effects on cardiac contractility, protein kinase A phosphorylation, and troponin I proteolysis.
Protein kinase A (PKA)-dependent phosphorylation is regulated by targeting of PKA to its substrate as a result of binding of regulatory subunit, R, to A-kinase-anchoring proteins (AKAPs). We investigated the effects of disrupting PKA targeting to AKAPs in the heart by expressing the 24-amino acid regulatory subunit RII-binding peptide, Ht31, its inactive analog, Ht31P, or enhanced green fluorescent protein by adenoviral gene transfer into rat hearts in vivo. Ht31 expression resulted in loss of the striated staining pattern of type II PKA (RII), indicating loss of PKA from binding sites on endogenous AKAPs. In the absence of isoproterenol stimulation, Ht31-expressing hearts had decreased +dP/dtmax and -dP/dtmin but no change in left ventricular ejection fraction or stroke volume and decreased end diastolic pressure versus controls. This suggests that cardiac output is unchanged despite decreased +dP/dt and -dP/dt. There was also no difference in PKA phosphorylation of cardiac troponin I (cTnI), phospholamban, or ryanodine receptor (RyR2). Upon isoproterenol infusion, +dP/dtmax and -dP/dtmin did not differ between Ht31 hearts and controls. At higher doses of isoproterenol, left ventricular ejection fraction and stroke volume increased versus isoproterenol-stimulated controls. This occurred in the context of decreased PKA phosphorylation of cTnI, RyR2, and phospholamban versus controls. We previously showed that expression of N-terminal-cleaved cTnI (cTnI-ND) in transgenic mice improves cardiac function. Increased cTnI N-terminal truncation was also observed in Ht31-expressing hearts versus controls. Increased cTnI-ND may help compensate for reduced PKA phosphorylation as occurs in heart failure.
McConnell
Bradley K
BK
Department of Physiology and Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA. bkmcconn@centreal.uh.edu
Popovic
Zoran
Z
Mal
Niladri
N
Lee
Kwangdeok
K
Bautista
James
J
Forudi
Farhad
F
Schwartzman
Raul
R
Jin
J-P
JP
Penn
Marc
M
Bond
Meredith
M
D054758:A Kinase Anchor Proteins / Q000235:genetics / Q000378:metabolism*; D000256:Adenoviridae; D000818:Animals; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism; D002316:Cardiotonic Agents / Q000494:pharmacology; D054746:Cyclic AMP-Dependent Protein Kinase Type II / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D051379:Mice; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology*; D009206:Myocardium / Q000378:metabolism*; D010455:Peptides / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D051381:Rats; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics / Q000378:metabolism; D013318:Stroke Volume / Q000187:drug effects / Q000502:physiology; D014161:Transduction, Genetic; D019210:Troponin I / Q000235:genetics / Q000378:metabolism*; D000099211:Phospholamban
D054758:A Kinase Anchor Proteins; D002135:Calcium-Binding Proteins; D002316:Cardiotonic Agents; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D007545:Isoproterenol; D010455:Peptides; D019837:Ryanodine Receptor Calcium Release Channel; D019210:Troponin I; D000099211:Phospholamban